MailCrab

Email test server for development, written in Rust.

Inspired by MailHog and MailCatcher.

MailCrab was created as an exercise in Rust, trying out Axum and functional components with Yew, but most of all because it is really enjoyable to write Rust code.

TLDR

docker run --rm -p 1080:1080 -p 1025:1025 marlonb/mailcrab:latest

Features

• Accept-all SMTP server
• Web interface to view and inspect all incoming email
• View formatted mail, download attachments, view headers or the complete raw mail contents
• Runs on all amd64 and arm64 platforms using docker
• Just a 7.77 MB docker image

Technical overview

Both the backend server and the fontend are written in Rust. The backend receives email over an unencrypted connection on a configurable port. All email is stored in memory while the application is running. An API exposes all received email:

• /api/messages return all message metadata
• /api/message/[id] returns a complete message, given its id
• /ws send email metadata to each connected client when a new email is received

The frontend initially performs a call to /api/messages to receive all existing email metadata and then subscribes for new messages using the websocket connection. When opening a message, the /api/message/[id] endpoint is used to retrieve the complete message body and raw email.

The backend also accepts a few commands over the websocket, to mark a message as opened, to delete a single message or delete all messages.

Installation and usage

To run MailCrab only docker is required. Start MailCrab using the following command:

docker run --rm -p 1080:1080 -p 1025:1025 marlonb/mailcrab:latest

Open a browser and navigate to http://localhost:1080 to view the web interface.

The default SMTP port is 1025, the default HTTP port is 1080. You can configure the SMTP and HTTP port using environment variables (SMTP_PORT and HTTP_PORT), or by exposing them on different ports using docker:

docker run --rm -p 3000:1080 -p 2525:1025 marlonb/mailcrab:latest

Usage in a docker-compose.yml file:

version: "3.8"
services:
    mailcrab:
        image: marlonb/mailcrab:latest
        ports:
            - "1080:1080"
            - "1025:1025"
        networks: [default]

Development

Install Rust and Trunk

# clone the code
git clone [email protected]:tweedegolf/mailcrab.git

# start the backend
cd backend
cargo run

# serve the frontend (in a new terminal window)
cd ../frontend
trunk serve

# optionally send test messages in an interval
cd ../backend
cargo test